Re: + mm-swap-add-cluster-lock-v5.patch added to -mm tree

[Michal Hocko <mhocko@kernel.org>]

On Wed 18-01-17 12:23:54, Andrew Morton wrote:
> On Wed, 18 Jan 2017 09:37:31 +0100 Michal Hocko <mhocko@kernel.org> wrote:
> 
> > On Tue 17-01-17 15:45:39, Andrew Morton wrote:
> > [...]
> > > From: "Huang\, Ying" <ying.huang@intel.com>
> > > Subject: mm-swap-add-cluster-lock-v5
> > 
> > I assume you are going to fold this into the original patch. Do you
> > think it would make sense to have it in a separate patch along with
> > the reasoning provided via email?
> 
> It should be OK - the v5 changelog (which I shall use for the folded
> patch, as usual) has
> 
> : Compared with a previous implementation using bit_spin_lock, the
> : sequential swap out throughput improved about 3.2%.  Test was done on a
> : Xeon E5 v3 system.  The swap device used is a RAM simulated PMEM
> : (persistent memory) device.  To test the sequential swapping out, the test
> : case created 32 processes, which sequentially allocate and write to the
> : anonymous pages until the RAM and part of the swap device is used.

But there are more reasons than the throughput improvements. I would
consider the full lockdep support and fairness more important. The
drawback is the memory footprint which should be mentioned as well.

That being said, I will not insist, I just thought that this would be a
nice incremental change and easier to understand later rather than
searching the archives...

So take all this as my 2c...

-- 
Michal Hocko
SUSE Labs

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